Microelectromechanical devices have become increasingly used for applications for which no comparable non-mechanical electronic device is available. Even for switching applications for optical communication, telemetry, and information processing systems, for which non-mechanical electronic devices do exist, a need for augmented capabilities is frequently met by microelectromechanical devices.
Nevertheless, as increasing numbers of devices are fit into ever-smaller spaces, optical microelectromechanical devices (hereinafter, "MEMS") and particularly their constituent actuatable MEMS elements present an increasing problem of sensing their respective actuated positions. One frequently used technique for handling this problem involves illuminating the constituent elements with infrared radiation, typically coherent radiation, detecting the pattern of reflected radiation with a high-resolution infrared video camera, and employing a computer to calculate the respective positions from the detected pattern. Unfortunately, as the number of MEMS elements in a given area increases, and as their speed of actuation increases, the computer software required for timely, accurate calculations becomes ever more complex and less reliable.
Such position detection techniques may be termed indirect techniques. It has become desirable to have reliable direct detection techniques.
While some MEMS sensors for directly detecting the position of a actuated element have been developed for some applications, their feasibility is not readily apparent for dense arrays of MEMS elements requiring a correspondingly dense array of electronic actuation circuits. Position sensing must not interfere with element actuation.